Description

Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component. This vulnerability was fixed in Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-15T13:16:49.447Z",
  "pubdate": "2026-09-15T13:16:49.447Z",
  "executiveSummary": "A critical privilege escalation vulnerability has been identified within the Graphics: CanvasWebGL component of the Mozilla Firefox browser. The flaw originates from incorrect boundary condition handling, which may allow a malicious actor to bypass security constraints and execute arbitrary code or gain unauthorized system privileges.\nThe vulnerability affects multiple releases, including Firefox 156, Firefox ESR 115.41, Firefox ESR 140.16, and Firefox ESR 153.3. By exploiting memory management errors during WebGL rendering operations, an attacker can transition from a sandboxed web content context to an elevated execution state.\nThis poses a severe risk to system integrity and user confidentiality, as successful exploitation could lead to full system compromise depending on the user's privilege level. Exploitation typically requires the victim to interact with a specially crafted webpage or application that triggers the flawed rendering logic. Organizations and individual users are urged to update to the latest patched versions immediately to mitigate the risk of exploitation by remote attackers.",
  "technicalDetails": "The root cause of this vulnerability lies in an improper boundary condition check within the Graphics: CanvasWebGL component. WebGL relies on low-level graphics APIs to render content; however, the bridge between the high-level JavaScript API and the underlying hardware acceleration layer requires robust input validation to prevent memory corruption. In this instance, the validation logic fails to correctly account for specific data structures or buffer offsets passed to the GPU driver.\nWhen the CanvasWebGL engine processes malicious shader code or malformed buffer data, it fails to enforce strict boundary limits. This results in an out-of-bounds access scenario. An attacker can manipulate these conditions to induce a heap-based buffer overflow or read-what-where primitive, which provides the necessary foundation for subverting the browser's security sandbox.\nThe attack flow begins when a victim navigates to a compromised or malicious webpage that invokes the vulnerable WebGL functions. The attacker supplies a payload designed to trigger the boundary condition failure during the allocation or copying of graphics memory. By precisely crafting the input, the attacker can overwrite critical internal structures within the browser process memory space.\nSuccessful exploitation allows for the redirecting of execution flow, enabling the attacker to bypass browser-enforced security policies and execute code with the permissions of the Firefox process. While the process itself may be sandboxed, the ability to escalate privileges from web content to the browser process significantly increases the threat level, potentially leading to further exploitation of kernel-mode components or local system resources.\nAffected versions include Firefox 156 and specific ESR builds: 115.41, 140.16, and 153.3. There are no authentication requirements for an external attacker, as the exploitation is triggered via standard web-based interaction. The vulnerability does not require physical access and can be exploited remotely over the network, making it a critical concern for all users of the affected versions.\nPost-exploitation impact includes persistent code execution, data exfiltration, or the installation of secondary malicious payloads, as the attacker effectively breaks the isolation mechanism designed to prevent untrusted content from accessing the underlying host system."
}